Minority impurity

Secondary amines give only a monosubstituted product. Both of these reactions are thermally reversible. The product with ammonia (3,3, 3 -nitrilottispropionamide [2664-61-1C H gN O ) (5) is frequently found in crystalline acrylamide as a minor impurity and affects the free-radical polymerisation. An extensive study (8) has determined the stmctural requirements of the amines to form thermally reversible products. Unsymmetrical dialkyl hydrasines add through the unsubstituted nitrogen in basic medium and through the substituted nitrogen in acidic medium (9)). 

Because the higher alcohols are made by a number of processes and from different raw materials, analytical procedures are designed to yield three kinds of information the carbon chain length distribution, or combining weight, of the alcohols present the purity of the material and the presence of minor impurities and contaminants that would interfere with subsequent use of the product. Analytical methods and characterization of alcohols have been summarized (13). 

Bromine ttifluoride is commercially available at a minimum purity of 98% (108). Free Br2 is maintained at less than 2%. Other minor impurities are HF and BrF. Free Br2 content estimates are based on color, with material containing less than 0.5% Br2 having a straw color, and ca 2% Br2 an amber-red color. Fluoride content can be obtained by controlled hydrolysis of a sample and standard analysis for fluorine content. Bromine ttifluoride is too high boiling and reactive for gas chromatographic analysis. It is shipped as a Hquid in steel cylinders in quantities of 91 kg or less. The cylinders are fitted with either a valve or plug to faciUtate insertion of a dip tube. Bromine ttifluoride is classified as an oxidizer and poison by DOT. 

Iodine pentafluoride is commercially available at a minimum purity of 98% (108). Iodine heptafluoride is the principal impurity and maintained at less than 2%. Free I2 and HF are minor impurities. Iodine pentafluoride is shipped as a Hquid in steel cylinders in various quantities up to 1350 kg cylinders. It is classified as an oxidizer and poison by DOT. 

For specific applications, other minor impurities may be requited to be controlled to limiting maxima by agreement between the purchaser and the seller. Includes elements for which no specific limit is shown. 

The extent of purification depends on the use requirements. Generally, either intense aqueous extractive distillation, or post-treatment by fixed-bed absorption (qv) using activated carbon, molecular sieves (qv), and certain metals on carriers, is employed to improve odor and to remove minor impurities. Essence grade is produced by final distillation in nonferrous, eg, copper, equipment (66). 

Phase diagrams can be used to predict the reactions between refractories and various soHd, Hquid, and gaseous reactants. These diagrams are derived from phase equiHbria of relatively simple pure compounds. Real systems, however, are highly complex and may contain a large number of minor impurities that significantly affect equiHbria. Moreover, equiHbrium between the reacting phases in real refractory systems may not be reached in actual service conditions. In fact, the successful performance of a refractory may rely on the existence of nonequilibrium conditions, eg, environment (15—19). 

Under typical chlorination conditions, most elements are chlorinated. Therefore, for every metric ton of titanium tetrachloride produced, lower grade feedstocks requite more chlorine. Minor impurities such as alkaline-earths, where the chlorides are relatively involatile, may either inhibit bed-fluidization or cause blockages in the equipment and requite particular consideration regarding feedstock specification. 

The Palmerton, Pennsylvania, plant had 43 retorts with an output of ca 8 t/d per retort. Recovery was ca 94% when the plant was shut down in 1980. The zinc contained ca 0.3% lead, 0.10% cadmium, and 0.01% iron plus minor impurities. Lead and aluminum are added to produce galvanizer s zinc. 

Extraction of Bertrandite. Bertrandite-containing tuff from the Spor Mountain deposits is wet milled to provide a thixotropic, pumpable slurry of below 840 p.m (—20 mesh) particles. This slurry is leached with sulfuric acid at temperatures near the boiling point. The resulting beryUium sulfate [13510-49-1] solution is separated from unreacted soflds by countercurrent decantation thickener operations. The solution contains 0.4—0.7 g/L Be, 4.7 g/L Al, 3—5 g/L Mg, and 1.5 g/L Fe, plus minor impurities including uranium [7440-61-1/, rare earths, zirconium [7440-67-7] titanium [7440-32-6] and zinc [7440-66-6]. Water conservation practices are essential in semiarid Utah, so the wash water introduced in the countercurrent decantation separation of beryUium solutions from soflds is utilized in the wet milling operation. 

In iadustrial production of titanium carbide, pure (99.8%, with minor impurities of Si, Fe, S, P, and alkahes) titanium oxide [13463-67-7] Ti02, iu the dry or wet state is mixed iu 68.5 31.5 ratio with carbon black or finely milled low ash graphite. The dry mixture is pressed iato blocks that are heated iu a horizontal or vertical carbon-tube furnace at 1900—2300°C hydrogen that is free of oxygen and nitrogen serves as protective gas. In the vertical push-type furnaces, the Hberated CO itself provides protection. 

Of the four commercial processes for the purification of carbon monoxide two processes are based on the absorption of carbon monoxide by salt solutions, the third uses either low temperature condensation or fractionation, and the fourth method utilizes the adsorption of carbon monoxide on a soHd adsorbent material. AH four processes use similar techniques to remove minor impurities. Particulates are removed in cyclones or by scmbbing. Scmbbing also removes any tars or heavy hydrocarbon fractions. Acid gases are removed by absorption in monoethanolamine, hot potassium carbonate, or by other patented removal processes. The purified gas stream is then sent to a carbon monoxide recovery section for final purification and by-product recovery. 

The use of ethyl alcohol ia some medicinal and cosmetic products requires a very meticulous grade, particularly with reference to odor. In some instances, the odor can be correlated with the concentration of certain minor impurities in most instances it caimot be direcdy associated with any measurable contaminant, and the quality can be ascertained only by odor comparison with previously accepted material. 

Generally, plastics have excellent resistance to weak mineral acids and are unaffected by inorganic salt solutions—areas where metals are not entirely suitable. Since plastics do not corrode in the electrochemical sense, they offer another advantage over metals most metals are affected by slight changes in pH, or minor impurities, or oxygen content, while plastics will remain resistant to these same changes. 

Aluminium fluoride (anhydrous) [7784-18-4] M 84.0, m 250°. Technical material may contain up to 15% alumina, with minor impurities such as aluminium sulfate, cryolite, silica and iron oxide. Reagent grade AIF3 (hydrated) contains only traces of impurities but its water content is very variable (may be up to 40%). It can be dried by calcining at 600-800° in a stream of dry air (some hydrolysis occurs), followed by vacuum distn at low pressure in a graphite system, heated to approximately 925° (condenser at 900°) [Henry and Dreisbach J Am Chem Soc 81 5274 1959]. 

The upshot of all this research since 1954 is rather modest, with the exception of the GE research, which indicates that techniques and individual materials have to be married up an approach which is crucial for one material may not be very productive for another. This is of course not to say that this 40-year programme of research was wasted. The initial presumption of the potential value of ultra-pure metals was reasonable it is the obverse of the well-established principle that minor impurities and dopants can have major effects on the properties of metals. 

Let us assume that a given compound has a purity of 98 % ee, and that this compound is reacted with a derivatizing agent which has also a purity of 98 % ee. The two major compounds plus the minor impurities in the compound to be analyzed and the derivatizing agent will create a set of four diastereomers. Two pairs of diastereomers (-i-)-A(-i-)B and (-)-A(-)-B as well as (- )-A(-i-)-B and (-i-)-A(-)-B are enantiomeric pairs, and thus elute together on an achiral column. Therefore, a peak area of 98.011 % will be detected for (-i-)-A(-i-)-B, which leads to a purity of 96.03 % ee for (-i-)-A. This is a quite significant deviation from the true value for (-i-)-A. 

Kubaschewski and Hopkins consider the conditions of the gaseous phase which influence the rate of corrosion of metals apart from major variations of composition, they refer also to the effects of minor impurities, gas pressure, flow rate and ionisation. 

It should also be emphasised that unless otherwise stated all reagents employed in the analytical procedures should be of appropriate analytical grade or spectroscopic grade materials. Similarly, where solutions are prepared in water this automatically means distilled or deionised water from which all but very minor impurities will have been removed. 

The checkers found that gas chromatographic analysis of one sample using a 305 cm. by 0.3 cm. column packed with 10% SF-96 on Chromosorb P operated at 70° with a 60 ml./minute helium carrier gas flow rate gave five minor impurity peaks, two at shorter retention times, and three at longer retention times. None of these impurities was present in greater than 1.1% total impurities wrere 3%. 

The aldehyde contains small amounts of the starting ester and the overreduced alcohol along with other minor impurities. It can be stored for short periods of time (1-2 days) in a freezer at -20°C without significant deterioration. However long term storage is not recommended. 

Methods of analysis for the determination of active matter and minor impurities in AOS are described in ASTM D3673-89. Included are methods for determination of moisture, sulfate, chloride, alkalinity, pH, color, and neutral oil. Some alternative instrumental methods are described briefly below. 

Our data give a rate constant of 4 X 10-13 cc. molecule-1 sec.,-1 assuming the production of N02- solely by this reaction. However, one must consider the probability that N02, present as a minor impurity or produced by pyrolysis or N20 of or near the hot filament, would react by Reaction 20. 

The copper remaining in lead after the above operation is removed by matte formation. Finely divided sulfur is added to molten lead at temperatures slightly above its melting point, and the melt is stirred continuously. Copper sulfide forms and floats on the surface, leaving the bullion substantially free of copper (less than 0.005%). The standard free energies of formation of cuprous sulfide and lead sulfide are about the same the observed separation must, therefore, be due to kinetic factors or to the influence of certain minor impurities that are present in the lead. 

The third method that we have used to prepare these diazaboracyclohexane systems is the transamination reaction of 1,3-diaminopropane with the bis(dimethyiamino)boryl compound 8 (eq 8). The solid products 12 and 13, which contain, respectively, two or three of the BN2C3 heterocycles linked by B-N bonds, could not be distilled (or crystallized), but they were thermally stable to at least 200°C. After minor impurities were removed from 12 by vacuum distillation and from 13 by washing with hexane, the structures were confirmed by1H, 13C, and 11B NMR spectroscopy. 

The purity is estimated to be 98% by NMR. Crude material is obtained with a mass balance in excess of theoretical. Minor impurities can be detected by 13C NMR having signals at 5 24.61, 25.36, and 34.84 which may be due to the presence of a small amount of internal olefin in the 10-undecenoic acid. 

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